1. Field of the Invention
The present invention relates to a maskless lithography apparatus, and in particular to a system and method for converting vector format pattern data for use by a lithography apparatus.
2. Description of the Related Art
A maskless lithography machine generates optical or particle beamlets for exposing a target. The machine requires pattern data for modulating the beamlets as they are scanned over the surface of the target. When exposing a target at very high resolution, a very large amount of pattern data is required to enable the scanning process.
The pattern data is usually initially generated in a vector format, such as a GDS-II or OASIS format, and is then usually converted into a bitmap format for modulating the beamlets. In the conversion from the vector format to a bitmap, it is advantageous to store the data in an intermediate data format to permit some processing to be performed in advance of exposing the wafer while not requiring a large storage capacity to store the voluminous fully converted pattern data. A vector format may be used as the intermediate vector format. A vector format permits complex manipulations to be performed on the pattern data, such as performing various types of corrections which may involve pattern shifting or scaling in two dimensions and involving multiple pixel or sub-pixel shifts.
However, a vector format has the disadvantage it is non-deterministic, so the amount of memory required to store the data is a function of the pattern data, and the actual memory requirement to store the pattern data cannot be determined in advance. This is a significant drawback in view of the very large size of the pattern data.